A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., comprising part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
Within a lithographic apparatus, many moving components are controlled with extremely high accuracy. For example, it is desirable in a scanner to control the position, velocity and acceleration of the support that supports the patterning device and the support that supports the substrate. The accuracy requirements are all the more stringent because the velocities and the accelerations required may be relatively high. Combined with the relatively large mass of such structures, which is desired in order to provide sufficient stiffness, the forces involved are high, with a result that it is difficult to provide an actuation system with the required accuracy. Therefore, in the presently known systems, a long-stroke stage is provided that may be moved relative to the base frame of the lithographic apparatus with the required velocity and acceleration. A short-stroke stage is mounted to the long-stroke stage and supports the substrate support or the support for the patterning device. The short-stroke stage, as its name suggests, has a limited range of movement. However, it is possible to control the accuracy of the position, velocity and/or acceleration of the substrate support or support for the patterning device to the required level of accuracy. Accordingly, the short-stroke stage is used to correct the inaccuracies that may be introduced by the long-stroke stage. These may be caused by, for example, cogging, motor force factor variations and external disturbance forces, for example caused by the vibration of other components within the lithographic apparatus and/or the connection of cables or conduits for gas supplies to the support for the substrate or patterning device.
However, in order to provide the desired accuracy, it is desirable that the short-stroke stage be able to provide relatively high accelerations. For example, a short-stroke actuator for a substrate support may need to accelerate a 20 kg substrate support up to an acceleration of 20 m/s2, requiring about 400 N of force. Consequently, the short-stroke actuator is relatively bulky and requires considerable thermal conditioning in order to avoid distortion of the substrate support and other temperature sensitive components due to heating.